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Kamgi kŏllin mulgogi
A school of fish splits apart over a rumor that one of them is sick, only to discover that they are safer together.
Book
Phosphorus dynamics in vegetated buffer strips in cold climates: A review
The movement of excess phosphorus (P) into streams, rivers and lakes poses a significant threat to water quality and the health of aquatic ecosystems and thus P has been targeted for reduction. In landscapes dominated by agriculture, P is primarily transported through non-point sources which a number of best management practices aim to target. One such practice is vegetated buffer strips (VBS), which are designed to use dense vegetation above the surface and extensive root systems below the surface to reduce runoff velocity, trap sediments, increase infiltration, and increase plant uptake of nutrients. The effectiveness of VBS in reducing P concentrations has been studied and reviewed, but most studies have been undertaken in warm or temperate climates, where runoff is primarily driven through summer rainfall events, and when vegetation is actively growing. In cold climates, the majority of runoff occurs during the snowmelt period when vegetation is not actively taking up nutrients, has been flattened by snow and ice over the winter period, and when soils are frozen. These conditions hinder the ability for VBS to work as designed. Additionally, frozen vegetation can release P after undergoing freeze-thaw cycles (FTCs). Thus, this review aimed to: i) summarize research designed to determine the effectiveness of VBS to reduce P transport undertaken in cold climates; ii) collate research on the potential for vegetation to release P after undergoing FTCs; and iii) identify research gaps to be addressed in determining VBS effectiveness in cold climates. Cold climate VBS implemented in Canada, the northern United States, and northern Europe have shown P removal efficiencies ranging from -36% to +89%, a range that pinpoints the uncertainty surrounding the use of VBS in these landscapes. However, there is consensus in research globally that vegetation does release P after undergoing FTCs, though P concentrations from different species vary across studies. The design and management of VBS in cold climates requires careful consideration and may not always be the best management strategy to reduce P transport. Future research should be undertaken at a larger scale in natural systems and focus on VBS design and management strategies.
Journal Article
Analysis of the DNA methylation of maize (Zea mays L.) in response to cold stress based on methylation-sensitive amplified polymorphisms
DNA methylation plays a vital role in tuning gene expression in response to environmental stimuli. Here, methylation-sensitive amplified polymorphisms (MSAP) were used to assess the effect of cold stress on the extent and patterns of DNA methylation in maize seedlings. Overall, cold-induced genome-wide DNA methylation polymorphisms accounted for 32.6 to 34.8% of the total bands at the different treatment time-points. It was demonstrated that the extent and pattern of DNA methylation was induced by cold stress through the cold treatment process and that the demethylation of fully methylated fragments was the main contributor of the DNA methylation alterations. The sequences of 28 differentially amplified fragments relevant to stress were successfully obtained. Under the cold stress, demethylation was detected in most fragments. BLAST results indicate that the homologues of these fragments are involved in many processes, including hormone regulation, cold response, photosynthesis, and transposon activation. The expression analysis demonstrated an increase in the transcription of five demethylated genes. Despite the fact that DNA methylation changes and cold acclimation are not directly associated, our results may indicate that the specific demethylation of genes is an active and rapid epigenetic response to cold in maize during the seedling stage, further elucidating the mechanism of maize adaptation to cold stress.
Journal Article
Transcriptional profiling of bud dormancy induction and release in oak by next-generation sequencing
Background
In temperate regions, the time lag between vegetative bud burst and bud set determines the duration of the growing season of trees (i.e. the duration of wood biomass production). Dormancy, the period during which the plant is not growing, allows trees to avoid cold injury resulting from exposure to low temperatures. An understanding of the molecular machinery controlling the shift between these two phenological states is of key importance in the context of climatic change. The objective of this study was to identify genes upregulated during endo- and ecodormancy, the two main stages of bud dormancy. Sessile oak is a widely distributed European white oak species. A forcing test on young trees was first carried out to identify the period most likely to correspond to these two stages. Total RNA was then extracted from apical buds displaying endo- and ecodormancy. This RNA was used for the generation of cDNA libraries, and in-depth transcriptome characterization was performed with 454 FLX pyrosequencing technology.
Results
Pyrosequencing produced a total of 495,915 reads. The data were cleaned, duplicated reads removed, and sequences were mapped onto the oak UniGene data. Digital gene expression analysis was performed, with both
R
statistics and the R-Bioconductor packages (edgeR and DESeq), on 6,471 contigs with read numbers ≥ 5 within any contigs. The number of sequences displaying significant differences in expression level (read abundance) between endo- and ecodormancy conditions ranged from 75 to 161, depending on the algorithm used. 13 genes displaying significant differences between conditions were selected for further analysis, and 11 of these genes, including those for glutathione-S-transferase (GST) and dehydrin xero2 (XERO2) were validated by quantitative PCR.
Conclusions
The identification and functional annotation of differentially expressed genes involved in the “response to abscisic acid”, “response to cold stress” and “response to oxidative stress” categories constitutes a major step towards characterization of the molecular network underlying vegetative bud dormancy, an important life history trait of long-lived organisms.
Journal Article
Two transcription factors, DREB1 and DREB2, with an EREBP/AP2 DNA binding domain separate two cellular signal transduction pathways in drought- and low- temperature-responsive gene expression, respectively, in Arabidopsis
Plant growth is greatly affected by drought and low temperature. Expression of a number of genes is induced by both drought and low temperature, although these stresses are quite different. Previous experiments have established that a cis-acting element named DRE (for dehydration-responsive element) plays an important role in both dehydration- and low-temperature-induced gene expression in Arabidopsis. Two cDNA clones that encode DRE binding proteins, DREB1A and DREB2A, were isolated by using the yeast one-hybrid screening technique. The two cDNA libraries were prepared from dehydrated and cold-treated rosette plants, respectively. The deduced amino acid sequences of DREB1A and DREB2A showed no significant sequence similarity, except in the conserved DNA binding domains found in the EREBP and APETALA2 proteins that function in ethylene-responsive expression and floral morphogenesis, respectively. Both the DREB1A and DREB2A proteins specifically bound to the DRE sequence in vitro and activated the transcription of the beta-glucuronidase reporter gene driven by the DRE sequence in Arabidopsis leaf protoplasts. Expression of the DREB1A gene and its two homologs was induced by low-temperature stress, whereas expression of the DREB2A gene and its single homolog was induced by dehydration. Overexpression of the DREB1A cDNA in transgenic Arabidopsis plants not only induced strong expression of the target genes under unstressed conditions but also caused dwarfed phenotypes in the transgenic plants. These transgenic plants also revealed freezing and dehydration tolerance. In contrast, overexpression of the DREB2A cDNA induced weak expression of the target genes under unstressed conditions and caused growth retardation of the transgenic plants. These results indicate that two independent families of DREB proteins, DREB1 and DREB2, function as trans-acting factors in two separate signal transduction pathways under low-temperature and dehydration conditions, respectively
Journal Article
Refrigeration nation : a history of ice, appliances, and enterprise in America
How we keep food cold while the house stays warm.
Only when the power goes off and food spoils do we truly appreciate how much we rely on refrigerators and freezers. In Refrigeration Nation, Jonathan Rees explores the innovative methods and gadgets that Americans have invented to keep perishable food cold—from cutting river and lake ice and shipping it to consumers for use in their iceboxes to the development of electrically powered equipment that ushered in a new age of convenience and health.
As much a history of successful business practices as a history of technology, this book illustrates how refrigeration has changed the everyday lives of Americans and why it remains so important today. Beginning with the natural ice industry in 1806, Rees considers a variety of factors that drove the industry, including the point and product of consumption, issues of transportation, and technological advances. Rees also shows that how we obtain and preserve perishable food is related to our changing relationship with the natural world.
eBook
Bright now. Beyond cold
The human body is a wonderfully complex machine and confronted to extreme conditions such as hypoxia, cold, and isolation, it triggers off strange and primitive survival mechanisms that modern science is only beginning to understand.
Streaming Video
Identification and abiotic stress response of a glutamine synthetase gene (AccGS) from the Asiatic honeybee, Apis cerana cerana (Hymenoptera: Apidae)
Glutamine synthetase (GS) is an essential detoxification enzyme that plays an important role in stress responses; however, little information regarding the function of this enzyme in hymenopteran insects is available. In the present study, we isolated and characterized the gene encoding GS in the Asiatic honeybee, Apis cerana cerana. Multiple alignments and a phylogenetic analysis of GS sequences showed that AccGS belongs to the GSII superfamily and clusters with invertebrate GSs. Real-time quantitative PCR data demonstrated that AccGS is expressed at all developmental stages and in all tissues, with the highest expression observed in the sixth larval instar and in the brain. Moreover, AccGS expression is highly regulated by environmental stress, including xenobiotic, temperature, and ultraviolet light stresses. A disc diffusion assay showed that the recombinant AccGS protein confers resistance to mercuric chloride (HgCl2) stress in E. coli. This suggests that AccGS may play multiple roles in early development and in environmental stress responses.
Journal Article